Chapter 7: Proteins Flashcards
describe the structure of a protein
Folded amino acid chains
describe the structure of an amino acid
Amino acids have 3 main groups
- Nitrogen containing amine group
- Carboxylic acid
- Side chain (Rx)
How many different amino acids are there?
21
Describe the primary protein structure
Amino acids bind together through peptide bonds to form a polypeptide (releases a water molecule)
Not yet a protein (must fold into next level of structure)
Describe the secondary protein structure
Hydrogen bonds between non-adjacent amino acids lead to the formation of alpha helices and beta-pleated sheets
Describe the tertiary protein structure
Interactions between amino acids side chains lead to further folding of the polypeptide chain; May result in a functional protein
Describe the quaternary protein structure
Several proteins in their tertiary structure bind to form a final protein; each one is called a protein subunit
How many amino acids are essential?
9
define: transamination
Process of making non-essential amino acids by modifying other amino acids
Define: conditionally essential amino acids
Conditionally essential amino acids: non-essential amino acids that become essential when the body cannot synthesize enough of them
Define: complete proteins and the sources
Complete proteins: foods that have all nine essential amino acids
- All animal sources and soy, quinoa, and buckwheat
Define: incomplete proteins and the sources
Incomplete proteins: foods missing 1 or more essential amino acids
- Plant sources
- The missing amino acids are called the limiting amino acid(s)
- Lysine is usually the limiting amino acid
What do animal sources of protein also have in terms of nutritional value?
- Have B vitamins, iron, zinc, calcium
- Lower in fiber, higher in saturated fat and cholesterol ( which increases risk of heart disease)
What do plant sources of protein also have in terms of nutritional value?
- Contain some B vitamins, iron, zinc, calcium
- Higher in fiber, unsaturated fats, and phytochemicals
What is the idea behind complementing proteins?
- Consuming a variety of foods to get all your amino acids
Define: amino acid pool
where we take amino acids from to compose a protein
Define: denatured protein
Denatured protein: lacks 3d structure and loses function
How does a denatured protein occur
Acids, heat, agitation all denature proteins
Describe protein digestion in the mouth
mechanical digestion: chewing
Describe protein digestion in the stomach
hydrochloric acid and pepsin begin the chemical digestion of protein; Proteins must be denatured and broken down into individual amino acids to be absorbed into the SI by active transport
Describe protein digestion in the small intestine
protease secreted from the pancreas into the small intestine and the enzymes from the microvilli break down polypeptides into amino acids, dipeptides, and tripeptides; transport proteins move the products of protein digestion into the mucosal cell. Similar amino acids use the same transporter; if there is an overabundance of one, it may block the absorption of another. dipeptides and tripeptides enter the mucosal cells and are then broken down into single amino acids. amino acids pass into the blood next and travel to the liver which regulates the distribution of amino acids to the rest of the body
What functions do proteins have (7)?
- body structure
- transport
- enzymes
- movement
- fluid balance
- protection from disease
- energy
What is the main structural protein?
Collagen: main structural protein; most abundant; very stiff and strong
tendon
What is elastin?
Elastin: another key structural protein that allows for elasticity; not as strong as collagen; makes up skin
Explain this protein function: transport (3)
- Protein tracks in cells allow substances to “walk” in the tracks and permit transport around the cell
- Hemoglobin transports oxygen around the body
- Protein channels and pumps regulate movement of ions and molecules into and out of the cell
Explain this protein function: movement
- Myosin and actin are proteins found in muscle
- Myosin proteins attach to actin proteins and kink their heads which causes muscle contraction and produces movemen
Explain this protein function: fluid balance
- Water is attracted to positive and negative charges of amino acids found in blood proteins
- This draws water into blood and out of extracellular space
- If blood proteins are low, fluid can build up in the extracellular space leading to edema
Explain this protein function: protection from disease
- Collagen in skin helps to restrict what can enter the body
- If infectious agents enter, proteins called antibodies stick to these agents and promote their removal limiting the harm they cause
How much energy comes from 1 gram of protein
4kcal
define: marasmus
Marasmus: energy and protein deficiency; aka wasting syndrome; promotes: anemia, dehydration, heart irregularities, body temperature dysregulation
define: kwashiorkor
Kwashiorkor: protein deficient but energy sufficient; distended, swollen abdomen but a slim appearance
How can protein promote a caloric deficit (3)?
- Promoting fullness
- Contributing to carbohydrate and lipid metabolism
- Requires more energy to digest and absorb it (thermic effect)
Fill in the blank: protein muscle synthesis increases ___ hours following weight training
24 hours
How many grams of essential amino acids in the first 2 hours following exercise encourages muscle growth?
10g
How much protein should athletes eat?
ACSM recommends increasing intake from 0.8g/kg to 1.2-2.0g/kg depending on intensity and load of training
Fill in the blank: In the bone, _____ forms a matrix that calcium hardens
collagen
How do proteins affect kidney health?
High protein diets tax the kidneys because they have more waste products to excrete
What are 3 ways we can assess protein quality
- Protein digestibility corrected amino acid score (PDCAAS)
- Digestible indispensable amino acid score (DIAAS)
- Protein efficiency ratio (PER)
Describe: Protein digestibility corrected amino acid score (PDCAAS)
- Compares amino acid content of food against standard amino acid profile (score from 0-1)
- Takes into account digestibility of protein
- Old industry standard but moving away from it; based on mice (checks feces to see if any left in the stool)
Describe: Digestible indispensable amino acid score (DIAAS)
- Measures how well amino acids are digested in the ileum and more closely estimates the amount of amino acids absorbed by the body
- Database still being built
Describe: Protein efficiency ratio (PER)
- How much weight an animal gains when consuming a specific amount of protein, divided by the amount of food it consumed
- Used in Canada
Fill in the blank: _______ have more total protein and ______ than processed meats
Game meets; tryptophan
Fill in the blank: Excessive supplementation (__________) does not promote further gains
> 1.62g/kg body weight
Define: Branched-chain amino acids (BCAA)
- Essential amino acids that have branched side chain
- Are 35-40% of dietary essential amino acids found in body protein
- Reduce muscle damage associated with weight training
What are the health benefits of a vegetarian diet (3)
- High in fibre and phytochemicals and low in saturated fats
- Vegetarians are more likely to have lower BMIs, total cholesterol, and LDL
- At lower risk for heart disease, cancer, and CVD mortality
What are the health risks of a vegetarian diet (3)
- Lower in vitamin D, omega-3 fatty acids, calcium, iron and zinc
- Vitamin B12 is only found in animal products
- Supplementation is recommended if these aren’t sufficient in diet
explain nitrogen levels and measuring proteins
- measuring nitrogen intake in the diet and output in urine can assess when someone is in a state of negative nitrogen balance, positive nitrogen balance (usually pregnancy), or at equilibrium
